A septic tank, as defined in Webster's, is "an underground tank in which waste matter is decomposed through bacterial action." If there is not enough "bacteral action" the tank simply can not function properly. Over time, sludge will build up in the bottom of the tank and the tank will need to be pumped out. There is no way to prevent some solid sludge from building up, but adding a product to your system to promote bacterial growth will help break down the solid material which will increase the time between pumpings.